Fiber-reinforced thermoplastic resins (FRTP) are light and excellent in strength. Out of these, long fiber-reinforced thermoplastic resins (LFRTP) containing long reinforced-fibers having a long fiber length are particularly excellent in terms of impact resistance and stiffness and are used in the form of strings, for example, as strings of a tennis racket.
As a method of manufacturing such a string-formed product of long fiber-reinforced thermoplastic resins (hereinafter, referred to as a “fiber-reinforced strand”), a method of causing a reinforced fiber bundle such as a plurality of glass rovings to pass through a resin bath means storing a molten thermoplastic resin, thereby impregnating the reinforced fiber bundle with the molten resin, and pulling out the reinforced fiber bundle after the resin impregnation from the resin bath means while twisting the reinforced fiber bundle about a bundle center is disclosed, for example, patent literatures 1 and 2.